Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be fluctuating, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
In Europe, the breeding population is estimated to number 99,600-195,000 pairs, which equates to 199,000-391,000 mature individuals (BirdLife International 2015). Europe forms c. 35% of the global range, so a very preliminary estimate of the global population size is 570,000-1,120,000 mature individuals, although further validation of this estimate is needed.
The population is suspected to be fluctuating owing to fluctuations in rodent prey populations and weather conditions (del Hoyo et al. 1999). The European population is estimated to be stable (BirdLife International 2015).
The species occupies open coniferous and mixed forest mainly in tall forest interior, dominated by conifers and often interspersed with beech (Fagus), aspen (Populus), birch (Betula) and other broadleaved trees used for nesting. It occurs in taiga and montane forest and in lowlands at upper and middle latitudes; in temperate zone ranging from 250–300 m in narrow cool and moist ravines to above 1,000 m in Alps (Holt et al. 1999). It is monogamous and breeds from April to July. The nest is in a tree cavity, either a natural hole or one excavated by a woodpecker; it will also make use of nestboxes. Debris is removed from the hole and no material is added to it (Mikkola 1983, Holt et al. 1999). Clutches are usually four to seven eggs. It feeds on small mammals, especially voles, although also shrews (Sorex), bats (Myotis) and mice (Micromys,Apodemus) and small birds (Holt et al. 1999). The species is mainly resident, although some dispersal occurs during winter and bad weather and low prey numbers can cause irruptive movements (Hagemeijer and Blair 1997).
Breeding densities and numbers can fluctuate significantly with weather conditions and rodent cycles. Despite large-scale deforestation in Finland, there is no evidence of population declines there, however in west Germany its disappearance in many areas has been linked to destruction of forests and the resulting changes in ecosystem, such as increases in the population of Tawny Owls (Strix aluco) at higher elevations (Holt et al. 1999). It is also thought that acid rain damage in conjunction with increasing forest disease will weaken trees to storm damage and result in changes in the ecosystem and increased predation from S. aluco (König et al. 2008).
Conservation Actions Underway
CITES Appendix II. EU Birds Directive Annex I. Bern Convention Appendix II. The species became extinct in the Black Forest (Germany) by 1967 so a captive-breeding programme was initiated in 1968. By 1995, 150 breeding territories had been established in the Black Forest (Holt et al. 1999).
Conservation Action Proposed
The species requires more research to inform conservation measures (König et al. 2008). Conservation of forest habitats, including the preservation of old trees and provision of nest boxes would be beneficial to this species.
Text account compilers
Ashpole, J, Butchart, S., Ekstrom, J.
BirdLife International (2019) Species factsheet: Glaucidium passerinum. Downloaded from http://www.birdlife.org on 25/05/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 25/05/2019.